Tectonic hazards Flashcards
What are the components of the internal structure of the earth. (In order from top most to bottom)
Crust Upper most mantle Asthenosphere Lower mantle Outer core Inner core
Talk about the movement of tectonic plates
- Convection currents are movements of heat within the mantle. Material in the mantle is heated by the core and, causing the mantle material to expand, rise and spread out beneath the plates.
- This causes the plates to be dragged along and moved away from each other.
- The hot mantle material then begins to cool slightly and therefore sinks, bringing the plates along with it.
- The sinking mantle material heats up again as it nears the core, thus the whole process repeats.
When does the slab pull force occur.
- The slab pull force occurs when the dense, sinking oceanic plate at the subduction zones pulls the rest of the plate behind it.
- The subducting plate drives the downward motion of the convection current.
- The other side of the subducting plates is where the mantle material rises and drives the rising portion of the convection currents,
What are some examples of divergent place boundaries
Types and some place specific examples
Types:
- Oceanic oceanic divergence
- Continental continental divergence
Place specific examples:
Southern boundaries of the Australian plates, southern and eastern boundaries of the pacific plates
Describe what happens during the oceanic oceanic divergence
- Magma from the rising part of the convection currents move laterally along the mantle layer, making them responsible to move the 2 oceanic plates away from each other, causing them to diverge.
- This results in fractures forming in between the two plates.
- Magma that is less dense would rise into these fractures and come into contact with the ocean water, thus losing heat and condenses, leading to the formation of mid oceanic ridges.
- The continuous swelling of magma along the mid oceanic ridges leads to the formation of undersea volcanoes. The continuous swelling then cools upon contact with the water and solidifies to form more layers, causing the undersea volcanoes to rise above sea level and therefore lead to the formation of volcanic islands.
Describe what happens during continental continental
divergence
- The magma from the rising part of the convection current moves laterally along the mantle layer, making them responsible for moving the two continental plates away from each other, causing them to diverge.
- The process of faulting then occurs where the two plates being dragged away from each other results in tension forces being formed between them, therefore resulting to the formation of fractures in the lithosphere.
- As the divergence continues, land segments would begin to sink along the faults formed due to gravity.
- The segment of land that has been lowered to the bottom can be referred to as the rift valley system, while the adjacent land masses taller than it are known as block mountains.
- When the rift valley lowers below sea level, it becomes a narrow shallow sea, which eventually becomes an elongated flat floored valley.
Describe how the oceanic oceanic plate convergence occurs.
- The magma from the rising part of the convection current moves laterally along the mantle layer, making them responsible for the 2 oceanic plates to move towards each other, causing them to converge.
- When the two oceanic plates converge and collide, the slightly denser oceanic plate will subduct beneath the less dense oceanic plate.
- This results in the formation of an oceanic trench.
- The mantle material of the subducted oceanic plate is in contact with immense heat from the mantle layer, causing it to melt. This forms the magma, which would rise through the fault lines and fractures formed in the crust due to the convergence.
- The magma then comes into contact with the ocean and therefore cools down and solidifies to form undersea volcanoes.
- Over time, a chain of these undersea volcanoes form on the seafloor. Due to the continuous swelling of the magma, these undersea volcanoes eventually rise above water to form volcanic islands and maybe even a volcanic arch.
Describe how continental continental plate convergence occurs.
- Heat from the rising part of the convection current moves laterally along the mantle layer due to the slab pull force, making it responsible for moving the 2 continental plates towards each other, causing them to converge.
- As both the continental plates are too thick and buoyant to subduct underneath each other, a portion of the plate might thrust under, causing the crust to thicken.
- As the continental plates are malleable in nature, the compressional force from the constant convergence of the two continental plates results in the folding and buckling of the crust
- This therefore results in the formation of fold mountains.
Describe how oceanic continental convergence occurs
- Magma from the rising part of the convection current moves laterally along the mantle layer due to the slab pull force, making it responsible for the oceanic plate and continental plate to move towards each other, causing an oceanic continental plate convergence
- The denser oceanic plate subducts beneath the buoyant and thick continental plate.
- As continental plates are malleable in nature, the compression forces formed from the convergence of these 2 plates results in the bulking and folding of the crust, forming fold mountains
- An oceanic trench is formed at the subduction zone.
- The silica and rich magma formed from the melting of the subducted oceanic plate rises to the surface through fractures on the continental plates, forming stratovolcanoes in the midst of the fold mountains.
What are the parts of a volcano
- Magma Chamber
- Conduit pipe
- Vent
- Crater
- Secondary pipe
- Secondary crater
What are the two types of volcanoes
Strato and Shield volcanoes
Where are strato and shield volcanoes formed
Strato: along the converging plate boundaries
Shield: along the diverging plate boundaries.
How are earthquakes formed
When two plates converge, the jagged and rough surface to lock onto each other. This causes a build up of energy. Once there is too much energy, the plates are not able to lock on anymore and therefore result in the sudden release of large amounts of energy in the form of seismic waves, which leads to vibrations in the earth and therefore causes earthquakes.
What are the factors that affect the extent of damage of the earthquakes
Level of preparedness Time of the day Soil condition Population density Distance from epicenter
What are the impacts of earthquakes and tsunamis
Loss of lives destruction of infrastructure destruction of properties Disruption of services Landslides (earthquake only)
